Noble metal duct for conducting a glass melt and method for conducting a glass melt

ABSTRACT

The double-walled noble metal duct ( 1 ) for conducting a glass melt has an outer noble metal pipe ( 1   b ) and an inner noble metal pipe ( 1   a ) extending within the outer pipe, so that an inner space ( 21 ) is formed within the inner pipe and an intermediate space ( 23 ) is formed between the inner pipe ( 1   a ) and the outer pipe ( 1   b ). The intermediate space is completely filled with glass melt when the double-walled noble metal duct conducts the glass melt when the outer pipe ( 1   b ) has an exhaust vent ( 4 ). The outer pipe ( 1   b ) also has a bottom outlet ( 7 ) communicating with the intermediate space for removal of oxygen bubbles formed on the outer wall. The noble metal duct can be used in glass conditioning and in the manufacture of glass articles that have polyvalent ion vacancies.

BACKGROUND OF THE INVENTION

[0001] The present invention relates to a noble metal duct or conduitfor conducting a glass melt and to a method for conducting a glass meltusing the noble metal duct or conduit.

[0002] The dissociation of water, which is present in a glass melt,forms hydrogen and oxygen gas. The hydrogen gas will diffuse through anoble metal pipe or duct wall to the exterior, when the hydrogen partialpressure outside of the glass melt is less than that in the melt. Anonequilibrium condition thus arises in the interior space in the pipeor duct, because of the escape of the hydrogen from it. The product thusobtained has undesirable bubbles.

[0003] A method of avoiding the formation of oxygen bubbles in a glassmelt during conduction of the glass melt is known and described in WO98/18731. A hydrogen excess pressure is produced in that method on theside opposite to the glass-contacting side. The hydrogen overpressureapplied from the outside minimizes the diffusion of hydrogen through thenoble metal. Because of that equilibrium is maintained and the formationof gas bubbles is presented.

SUMMARY OF THE INVENTION

[0004] It is an object of the present invention to provide an apparatusand method for conducting and conditioning glass, in which gas bubbleformation is minimized.

[0005] This object is attained, in part, by a double-walled noble metalduct for conducting a glass melt, which comprises an outer noble metalpipe and an inner noble metal pipe extending within the outer noblemetal pipe, so that the noble metal duct has an inner space within theinner noble metal pipe and an intermediate space between the inner noblemetal pipe and the outer noble metal pipe. The intermediate spacebetween the inner and outer pipes of the double-walled noble metal ductis filled with a glass melt when the double-walled noble metal ductconducts a glass melt.

[0006] In preferred embodiments of the invention platinum or platinumalloy is used as the noble metal according to the invention.

[0007] The double-walled noble metal duct according to the invention hasan exhaust vent and a bottom outlet both communicating with theintermediate space. Because of the exhaust vent it is possible tocompletely fill the intermediate space between the inner and outer wallsof the noble metal duct. Oxygen formed on the outer pipe can be drawnoff through the bottom outlet.

[0008] The above object is also attained, in part, by a method forguiding a glass melt through a duct system comprising the double-wallednoble metal duct, so that the glass melt is free of oxygen bubbles. Thenoble metal duct is a double-walled pipe having an inner wall and anouter wall both made of the noble metal, so that an inner space isformed within the inner wall and an intermediate space is formed betweenthe outer wall and the inner wall. The intermediate space between theinner wall and the outer wall is filled with glass melt when glass meltis conducted through the double-walled noble metal duct, as explainedabove.

[0009] The invention also comprises a method of guiding and conditioninga glass melt, including conducting the glass melt through adouble-walled noble metal duct or pipe.

[0010] In addition, the invention further comprises a method ofpreparation of glass articles having polyvalent ion vacancies.

BRIEF DESCRIPTION OF THE SOLE FIGURE

[0011] The objects, features and advantages of the invention will now beillustrated in more detail with the aid of the following description ofthe preferred embodiments, with reference to the accompanying solefigure showing an example of the double-walled noble metal duct forconducting a glass melt according to the invention.

DETAILED DESCRIPTION OF THE INVENTION

[0012] A duct system is shown in the sole figure, which comprises anoble metal double-walled duct 1. The double-walled noble metal duct 1comprises an outer noble metal pipe 1 b and an inner noble metal pipe 1a extending within the outer noble metal pipe 1 b. In this embodimentthe inner noble metal pipe 1 a and the outer noble metal pipe 1 aconsist of platinum metal.

[0013] In the embodiment shown in the sole figure the glass melt flowsfrom a distributor or working pan through a flow stone or melt outletmember 2 into the double-walled noble metal duct 1. The inner space 21in the noble metal duct 1 and the intermediate space 23 between theinner noble metal pipe 1 a and the outer noble metal wall 1 b are filledwith the glass melt when the duct 1 conducts a glass melt. The glassmelt flows into the upstream entrance or beginning 3 of the intermediatespace 23 into the intermediate space; the opposite or downstream end 33of the intermediate space 23 is advantageously closed. Since thehorizontal portion of the duct 1 has an exhaust vent 4 communicatingwith the intermediate space, the complete access to the intermediatespace 23 is guaranteed. The glass melt flows unhindered to the target ordestination vessel 5 through the inner space 21 of the double-wallednoble metal duct 1, since the glass melt flows out through the glassoutlet 6. Oxygen bubbles, which form on the outer noble metal wall 1 b,for example at position 10, can be removed by means of a bottom outlet 7communicating with the intermediate space. The entire double-wallednoble metal duct 1 is heated by means of an electrical heating circuit8. The interior and outer noble metal pipes 1 a, 1 b are connected byconnecting pieces or cross members 9.

[0014] The nonequilibrium reaction according to equation I takes placewhen different hydrogen partial pressures are present on respectivesides of the noble metal duct 1. Platinum is known to be permeable tohydrogen. When the hydrogen partial pressure outside of the melt is lessthan that in the melt, the hydrogen diffuses through the platinum wallsof the pipe. Nonequilibrium according to equation I arises in the melt.This nonequilibrium leads to formation of oxygen bubbles in the melt.The product so obtained has undesirable bubbles.

[0015] According to the invention the equilibrium reaction according toformula 11 takes place in the inner space of the double-walled noblemetal duct 1. The glass between the noble metal pipes 1 a, 1 b preventsthe diffusion of the hydrogen through the inner noble metal wall 1 a.The equilibrium remains present during water dissociation, since equalhydrogen partial pressures exist on both sides of the noble metal innerwall 1 a. Thus no oxygen bubbles form.

[0016] The equations I and II are:

H₂O→1/2 O₂+H₂  I

H₂O⇄1/2 O₂+H₂  II.

[0017] The disclosure in German Patent Application 101 41 585.0-45 filedon Aug. 24, 2001 in Germany is incorporated here by reference. ThisGerman Patent Application describes the invention described hereinaboveand claimed in the claims appended hereinbelow and provides the basisfor a claim of priority for the instant invention under 35 U.S.C. 119.

[0018] While the invention has been illustrated and described asembodied in a double-walled noble melt duct or pipe for conducting aglass melt, it is not intended to be limited to the details shown, sincevarious modifications and changes may be made without departing in anyway from the spirit of the present invention.

[0019] Without further analysis, the foregoing will so fully reveal thegist of the present invention that others can, by applying currentknowledge, readily adapt it for various applications without omittingfeatures that, from the standpoint of prior art, fairly constituteessential characteristics of the generic or specific aspects of thisinvention.

[0020] What is claimed is new and is set forth in the following appendedclaims.

We claim:
 1. A double-walled noble metal duct (1) for conducting a glassmelt, said double-walled noble metal duct comprising an outer noblemetal pipe (1 b) and an inner noble metal pipe (1 a) extending withinthe outer noble metal pipe, so that an inner space (21) is formed withinthe inner noble metal pipe, an intermediate space (23) is formed betweenthe inner noble metal pipe (1 a) and the outer noble metal pipe (1 b),and said intermediate space is filled with glass melt when the glassmelt is conducted through the inner space (21).
 2. The double-wallednoble metal duct as defined in claim 1, further comprising an exhaustvent (4) communicating with said intermediate space (23), so that saidintermediate space (23) completely fills with the glass melt duringconduction of the glass melt.
 3. The double-walled noble metal pipe asdefined in claim 1, further comprising a bottom outlet (7) communicatingwith said intermediate space (23) for removal of oxygen bubbles formedon the outer noble metal pipe (1 b).
 4. The double-walled noble metalduct as defined in claim 1, wherein said outer noble metal pipe and saidinner noble metal pipe are both made of platinum metal or platinumalloy.
 5. The double-walled noble metal duct as defined in claim 1,wherein said intermediate space (23) has an upstream entrance (3)through which said glass melt enters said intermediate space (23) butsaid intermediate space (23) is closed at a downstream end (33) thereof.6. A double-walled noble metal duct (1) for conducting a glass melt,said double-walled noble metal duct comprising an outer noble metal pipe(1 b) and an inner noble metal pipe (1 a) extending within the noblemetal outer pipe, so that an inner space (21) is formed within the innerpipe and an intermediate space (23) is formed between the inner noblemetal pipe and the outer noble metal pipe, said intermediate spacehaving an entrance (3) at an upstream end thereof and being closed at adownstream end (33) thereof; wherein said outer noble metal pipe (1 b)has an exhaust vent (4) communicating with said intermediate space (23)so that said intermediate space (23) completely fills with said glassmelt when said glass melt is conducted through the inner space (21) anda bottom outlet (7) communicating with said intermediate space (23),whereby oxygen bubbles formed on said outer noble metal wall (1 b) areremoved.
 7. A method of oxygen-free conduction of a glass melt through aduct system, said method comprising the steps of: a) providing adouble-walled noble metal duct (1) through which said glass melt is toflow in said duct system, wherein said double-walled noble metal ductcomprises an outer noble metal pipe (1 b) and an inner noble metal pipe(1 a) extending within the outer noble metal pipe, so that an innerspace (21) is formed within the inner noble metal pipe and anintermediate space (23) is formed between the inner noble metal pipe (1a) and the outer noble metal pipe (1 b), said intermediate space (23)having an upstream entrance (3) for said glass melt; b) conducting saidglass melt through said inner space (21) of said double-walled noblemetal duct (1) so that said intermediate space (23) fills with saidglass melt; and c) removing bubbles formed on said outer noble metalpipe (1 b) during the conducting of said glass melt through said innerspace (21).
 8. The method as defined in claim 7, wherein said outernoble metal pipe and said inner noble metal pipe are both made ofplatinum metal or platinum alloy.
 9. A method of guiding andconditioning a glass melt, said method comprising the steps of: a)providing a double-walled noble metal duct (1) through which said glassmelt is to flow in said duct system, wherein said double-walled noblemetal duct comprises an outer noble metal pipe (1 b) and an inner noblemetal pipe (1 a) extending within the outer pipe, so that an inner space(21) is formed within the inner noble metal pipe and an intermediatespace (23) is formed between the inner noble metal pipe (1 a) and theouter noble metal pipe (1 b), said intermediate space (23) having anupstream entrance (3) for said glass melt; b) conducting said glass meltthrough said inner space (21) of said double-walled noble metal duct (1)so that said intermediate space (23) fills with said glass melt; and c)removing bubbles formed on said outer noble metal pipe (1 b) during theconducting of said glass melt through said inner space (21).
 10. Amethod of producing a glass article with polyvalent ion vacancies, saidmethod comprising the steps of: a) providing a double-walled noble metalduct (1) through which a glass melt is to flow in said duct system,wherein said double-walled noble metal duct comprises an outer noblemetal pipe (1 b) and an inner noble metal pipe (1 a) extending withinthe outer pipe, so that an inner space (21) is formed within the innernoble metal pipe and an intermediate space (23) is formed between theinner noble metal pipe (1 a) and the outer noble metal pipe (1 b), saidintermediate space (23) having an upstream entrance (3) for said glassmelt; b) conducting said glass melt through said inner space (21) ofsaid double-walled noble metal duct (1) so that said intermediate space(23) fills with said glass melt; c) removing bubbles formed on saidouter noble metal pipe (1 b) during the conducting of said glass meltthrough said inner space (21); and d) making the glass article from theglass melt.